Various aluminophosphate compositions are known in the art. These compositions can exhibit widely different physical properties such as surface area, pore size and pore size distribution. The terms aluminophosphate compositions, supports and precipitates are used interchangeably herein.
Many aluminophosphate compositions lack a combination of physical properties which characterize superior polymerization catalyst supports. For example, some aluminophosphate compositions exhibit low surface area and poor heat stability. Other supports with a high macropore volume do not exhibit good physical stability.
Other supports lack sufficient activity to be suitable catalysts. Previous methods employed a cocatalyst to boost activity; however, the presence of the cocatalyst increases the amount of undesirable low molecular weight portion in the polymer product. This low molecular weight material causes problems, such as smoking, during subsequent processing.
Other catalysts are not effective at incorporating comonomer during polymerization. Still other catalysts produce a polymer having a relatively broad molecular weight distribution, while some applications require a narrow molecular weight distribution.